1. Field of the Invention
This invention relates to a method of assessing damage to human hair, and more particularly, to a method of quantifying human hair damage caused by hair treatment compositions applied thereto and damage caused to human hair by the environment.
2. Description of the Prior Art
Hair care is one of the most important part of beauty care, a large variety of hair treatment products are used for providing such care in the form of pre-shampoo conditioners, shampoos, after-shampoo conditioners, rinses, setting lotions, sprays, dyes, bleaches, permanent wave agents and the like. These products in addition to providing the desired result in the hair, such as luster, curl, combability, softness, color and an overall appealing look, also do damage to the hair, especially when used indiscriminantly without professional guidance. Damage to hair may also result from other sources, such as combing, humidity, dryness, dirt, sunrays, such as u.v. and infrared radiation, and pollution in the atmosphere. However, damage to hair occurs mostly in the form of physical and chemical changes in hair as a result of bleaching, oxidative dying, hair relaxing via alkaline relaxers and reducing waving and curling preparations.
Assessment of hair damage is desirable, so that corrective action may be taken. Such corrective action may be: the utilization of products which do not cause damage or their damaging affect is minimal; eliminating the use of deleterious products; using products in proper sequence to circumvent further damage; or using products designed to repair hair damage.
Measurement of hair damage is known in the prior art. For example, W. W. Edman and M. E. Marti, Journal of the Society of Cosmetic Chemists, pp: 133-145, Sept. 1960, report a study on properties of peroxide-bleached hair and use as a measure of hair damage the so-called 20% index, which is the ratio of work required to stretch the fiber 20 percent after treatment with a peroxide bleach to the work required to stretch the fiber 20% before treatment. To measure the 20% index a constant Elongation Tester is used. The same study also shows measurement of hair damage by "extension-at-break" using a Scott Tester.
Measurement of hair damage via copper absorption is also known. U.S. Pat. No. 4,263,277 discloses a method for measuring hair damage by soaking a known weight of hair sample in a 0.1 N tetraamine copper sulfate, followed by washing with water. The filtrate is then titrated against 0.1 N sodium thiosulfate to determine the amount of copper absorbed by the hair. The damage to hair is assumed to correlate with the amount of copper absorbed by the hair sample.
While methods like these to assess hair damage are appropriate for investigational and research purposes, they are not suitable for use by hair-care professionals or for home use.
It is an object of the present invention to provide a method which can be easily applied by hair-care professionals as well as individuals to assess hair damage.
It is another object of the present invention to provide a simple device for measuring the volume of fibrous materials as well as measuring the volume of hair samples used in the method of assessing hair damage.
It is still another object of the present invention to provide stable copper solutions suitable for use in the method of assessing hair damage.
These and other objects are accomplished in accordance with the following description of the invention.